The invention relates to a grinding center for grinding crankshafts having main bearings and pin bearings, a plurality of main bearings and pin bearings as well as end-side surfaces, especially of a flange, being ground essentially simultaneously.
Such grinding centers are used for rough-grinding and/or finish-grinding of large numbers of crankshafts. These are often crankshafts for four cylinder in-line engines in the automobile industry, in which engines each of two pin bearings are arranged at the same angular position with respect to the longitudinal axis of the crankshaft. These two pin bearings are ground simultaneously (time parallel) in order to increase productivity. One such procedure is described for instance in EP 1 044 764 A2 and EP 1 088 621 B1.
Simultaneously grinding a plurality of bearings has been known for some time for the main bearings of crankshafts, e.g., from U.S. Pat. No. 3,487,588. The grinding spindle for the main bearings has a number of grinding wheels that is equal to the number of main bearings. The grinding wheels are disposed on a common axis. A more recent version of this can be found in DE 101 44 644 B4.
In the grinding center for crankshafts in accordance with EP 1 044 674 A2, used for simultaneous grinding of two pin bearings on a crankshaft are a rough-grinding wheel and a finish-grinding wheel that are each securely mounted to discrete compound slide rests via the associated grinding spindle. The two compound slide rests can be moved independently of one another in the crankshaft longitudinal direction (Z direction) and can be adjusted relative to the crankshaft (X direction). Appropriately controlling the compound slide rests and the grinding spindles makes it possible to machine two pin bearings simultaneously in one clamping process, the one pin bearing being pre-ground and the other being finish-ground. The grinding process is monitored continuously via associated measuring devices.
EP 1 088 621 B1 describes a method and an apparatus for simultaneously grinding at least two bearings on a crankshaft that is essentially the same as the grinding center depicted in EP 1 044 764 A2 in terms of design and operation. Each of these systems uses a discrete compound slide rest for each of the two grinding spindles used. Each of these compound slide rests requires separate activation for the entire grinding process and continuous monitoring and correction according to real-time data, acquired via measuring heads, about the roundness and dimensions of the ground bearing. Simply in terms of the machining two bearings, the design of the grinding center with two separate compound slide rests requires a great deal of space and significant complexity with regard to components and associated controls.
EP 1 718 435 B1 describes a machine for machining workpieces in which machine grinding and/or turning apparatus are present. The grinding apparatus has a profiled grinding wheel that is inclined relative to the Z axis and by means of which the workpiece can be both face ground and also externally cylindrically ground. The tool is turned and ground in the same clamping.